Calculate the letter-spacing value

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Once you know your tracking numbers, use the following formula to calculate it:

Font AV (tracking) value ÷ 1000 = letter-spacing (em value)
If you apply the example numbers to the formula, the answer will be "0.08", so when coding, specify "letter-spacing: 0.08em;" in your CSS.

80 ÷ 1000 = 0.08em
Why do we use x1000 (÷1000) for character spacing calculations?
This time, when calculating the spacing between characters, the numbers "×1000" and "÷1000" came up, but I was curious as to why it was "1000," so I investigated.

How to specify character argentina number data spacing (tracking) in Adobe XD: "milli-em"
The Adobe XD User Guide states that character spacing should be changed to "milli-em" units as follows.
The following is an excerpt from the relevant section of the Adobe XD User Guide page.

Reference: Adobe XD User Guide > Drawing and Text Tool Operations > Text Formatting

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To change character spacing within a subset of text, select the text and change the character spacing in milli-ems using the Property Inspector.

What is "milli-em"?
I looked up the meaning of "milli-em."
Below is an excerpt from the relevant page on the Weblio English-Japanese/Japanese-English Dictionary.

Reference: weblio English-Japanese dictionary

fig14

Meaning "1/1000 of..."

In other words, "milli-em" means 1/1000em.
Since this formula can be applied not only to XD but also to Photoshop etc., I checked Adobe's user guide.

The following is an excerpt from the Photoshop User Guide page.

Reference: Photoshop User Guide > Text > Line and Character Spacing "Kerning and Tracking"

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Tracking and kerning values ​​are specified in 1/1000 of an em relative to the current type size ( 1 em is 6 points in a 6-point font, 1 em is 10 points in a 10-point font, etc. Kerning and tracking values ​​are always relative to the current type size.

Reference: Illustrator User Guide > Adding and Editing Content > Character > Line Spacing and Character Spacing "Adjusting Kerning and Character Spacing"

fig13

Tracking and kerning values ​​are specified in 1/1000 of an em relative to the current typeface size ( 1 em is 6 points in a 6-point font, 10 points in a 10-point font, etc. Kerning and tracking are relative to the current typeface size.

From the above, we can see that the tracking (AV, VA) values ​​are specified in units of 1/1000em based on the character size, so the formula for calculating the character spacing we wanted to calculate is "x 1000 (÷ 1000)."